Dry contact rectifier plate



Dec. 22, 1931. w. T. ANDERSON, JR, ET AL 1,838,068

DRY vCONTACT RECTIFIER PLATE I Filed Aug. 7, 1950 *7 3& P

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Patented Dec. 22, 1931 more!) STATES PATENT OFFICE WILLIAM '1. ANDERSON, JR, AND LESTER I. BIRD, OFQHEWABK, JERSEY, AS SIGNOBS T0 HANOVIA CHEMICAL AND EANUFAGI'UBLHVG comm, OF NEWARK, NEW JERSEY, A CORPORATION OF NEW JERSEY DRY CONTACT BEOTHIER PLATE Application filed August 7, 1980. Serial No. 473,732.

This invention relates to dry contact rectifier plates, and more particularly to the construction and shape 0 such plates.

Heretofore, in the manufacture, of coppercopper oxide rectifier plates, it has been the practice to provide each plate with a mounting hole in the center. This hole is also employed for mounting the plates while they are at an elevated temperature during the production of the oxide thereon.

The provision of the center hole has been found objectionable for the reason that during the cooling process the oxide on the edges of the hole is subjected'to great'strains resulting in nearly all .cases,.that portions of the oxide break away, baring the under.

medium of copper, a condition which lowers the efliciency of the plate as a rectifier by increasing the leakage current in the reverse direction. Y

It has been found that the edges of rectifier plates of this type are responsible for most of the back current of the plate.

While it is not definitely known why rectification occurs at the metal-oxide junction in such plates, it is well known that any mechanical damage to the oxide layer results in,

leakage and inelficient rectification. It may be readily understood that the amount of edge in a plate is increased when a hole is cut therein, and the possibility of leakage is enhanced thereby. Furthermore, the strains existing in a curved edge are considerably greater than those in a straight edge, and the leakage is correspondingly greater. It is, therefore, very desirable that there be no holes in the working or rectifying portion of the plates.

A finished rectifier plate consists of a copper central portion usually about .025 inch thickness, a layer of cuprous oxide on each side usually .008 inch thickness and a reduced or deposited metallic layer on the oxide about .0004 inch thickness. Contact electrically is made between the inner copper and the external circuit, and between the reduced layer and the external circuit. The flow of current is from outer metallic layer through the oxide to the central copper. Since the electrical conductivity of any metal is consider vshown in the accompanyin ably greater than that of the oxide and since a metal has a faculty of conduction in either direction, it is obvious that any metal making contact between the outer layer of a plate and the central copper will short circuit the plate, and make it worthless as a rectifier.

' When prepared copper plates are placed in a furnace for the production of cuprous oxide thereon, it is necessary to support the plates in some manner. Because of the high temperature of the furnace, approximately 1060 0., there exist but a few substances which may be used for supporting purposes and not be subjected to oxidation and destruction.

Practically all possible supporting substances are oxidized and destroyed under the conditions existing in the copper oxide rectifier plate furnace; and since, obviously, the support for the copper plate must touch the copper while hot, portions of the supporting material will become intermingled with the copper at the point of contact, as almost all known suitable supporting substances are attacked by copper under furnace conditions as set forth above.

Since. the mixture of the copper and the support material will not produce a rectifying contact such as exists between the copper and the oxide, it is necessary to remove the contaminating supporting material after the plate has been formed. Where there is a mounting hole in the center of'the plate, and this hole is em loyed for supporting the plate while in the urnace, the contamination occurs on the'edge of the hole, and must, in most cases, be ground away before the plate may be used as a rectifier.

It is an object of this invention to provide a rectifier plate having no mounting or supporting holes in the working or rectifying area'of the plate.

This and other objects are attained by the novel construction hereinafter described and drawings, constituting a material part 0 this disclosure, and in which:

Figure 1 represents a plan view of a rectifier plate embodying the invention.

Figure 2 represents a sectional View takenon line 22 of Figure 1.

Figure 3 represents a plan view of a rectifier plate embodying a modified form of the invention.

Referring to the drawings, a substantially rectangular plate 4 is shown to have at an upper corner a projection 5 having an aperture 6. In order to facilitate the manufacture of the plates and eliminate waste of metal, the plates are stamped from a sheet of copper, and the opposite upper corner of each plate is cut away at 7 the area of the cut-away portion beingequal to the area of the projection 5.

The aperture 6 is just large enough for the admission of a supporting hook for suspending the plate in a furnace. After the copper plate has been coated with copper oxide, the oxide is removed from the prQ ection 5 and direct electrical connection with the inner copper layer is enabled. It will be seen that projection 5 is easily accessible for connection purposes, and that at the same time the oxide is removed for makin the direct connection, the contamination rom the supporting material is also removed.

The aperture 6, therefore, is employed as a means for accommodating a supporting hook, and also as an anchor point for anexternal lead wire.

In Figure 2 is shown a modified form in which the plate is substantially rectangular in shape, and instead of providing a projection at an upper corner, an aperture 9 is drilled in the corner and the oxide removed ing to be removed and the contaminationfrom the furnace eliminated by a single operation, for electrical contact to the inner copper laye'r is made at the corner or on the pro ection which is in contact with the furnace support hook. The oxide is removed around the hole for the external connection and this at the same time removes the damaged point caused by the supporting hook.

The foregoing disclosure is to be regarded as descriptive and illustrative only, and not as restrictive or limitative of the invention, of which an embodiment may be constructed including modifications without departing from the general scope herein indicated and denoted in the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent, is:

1. A dry contact rectifier plate of substantially rectangular form having a projection at one corner thereof and a cutaway portion at an opposlte corner, said projection being 

